This application is submitted to obtain support for the further investigation of the biosynthesis of pulmonary disaturated lecithin and for the study of factors which control the rate of lung lecithin synthesis. The pathways by which the lung synthesizes disaturated lecithin will be studied in lung slices and subcellular organelles in the adult and developing mammal using dual labeled 1,2 diglycerides synthesized in our laboratory. Variations in the placement of palmitic and oleic acid at the C-1 and C-2 positions on glycerol will permit an assessment of diglyceride preference. Analysis of the product lecithin will indicate whether the Kennedy and/or Land's lecithin synthetic pathways are most significant in disaturated lecithin synthesis in the lung. Additional studies will correlate oxygen consumption and type II alveolar cell turnover with lecithin synthesis.